5. Propagation
Viruses are spread from person to person, causing new cases of the disease. Many of them, as those responsible for influenza and measles, are transmitted by inhalation, through its dissemination in the infected droplets emitted by coughing and sneezing. Others, like those that cause diarrhea are spread by fecal-oral route. In other cases, the spread is through the bite of insects, such as yellow fever and arboviruses. Viral diseases may be endemic (specific to one area), affecting susceptible individuals, or epidemic, which appear in waves and attack much of the population. An example is the emergence of epidemic flu worldwide, almost always once a year.
6. Treatment
The treatments against viral infections are often not entirely satisfactory, since most of the drugs that kill viruses also affect cells in which they play. The alpha-adamantanamine is used in some countries to treat respiratory infections caused by influenza A and isatin-beta-thiosemicarbazone, effective against smallpox. Certain substances similar to precursors of nucleic acids may be useful against severe herpes infections. (more…)
